The present invention relates to a ball valve and method for dumping catalyst fines from a catalyst regenerator such as in the fluidized catalyst cracking (FCC) units of refineries.
In a refinery reactor operating at elevated temperatures and pressures, catalyst is used in the preparation of useable hydrocarbon molecules. Specifically, the catalyst helps to break down larger hydrocarbon molecules into smaller hydrocarbon molecules, thereby producing “lighter” hydrocarbons for further processing. Over time, catalyst in FCC units becomes coated with carbon (also known as coke) and ceases to efficiently break down the larger hydrocarbon molecules. The coked catalyst is transported to a regenerator reactor where it is heated with oxygen to burn off the coke and regenerate the catalyst. During normal operation and regeneration, some catalyst is broken into smaller particles, known as fines, and must be periodically replaced. A discharge piping system is used to dump the catalyst fines. The ball valve and method of the present invention can be used with such a piping system.
Extraction of catalyst fines has been performed using wear resistant choke tubes of a specific size selected to establish proper flow rates for the process requirements. The tube periodically plugs up with solids, requiring the line to be isolated and the tube removed and cleaned. Isolation is achieved by closing the upstream block valves, resulting in plant down time as well as added maintenance expenses.
An alternate approach has been to use a valve in place of the choke tube, and to throttle and control the flow of catalyst with the valve. This system has the advantage of having the capability for adjusting the flow, however the internals of the throttling valve wear rapidly and are expensive to replace.
Fisher (U.S. Pat. No. 3,386,461) discloses a multi-port orifice valve, adapted for cleaning of the bores of the valve, that uses interchangeable inserts which may be placed within the bore of the valve. The valve body features four apertures (two per side), positioned to allow servicing (cleaning of the bore as well as removal and reinsertion of orifice inserts) while the particular bore is in the closed position, without having to shut down the line and remove the valve.
Crawford (U.S. Pat. No. 3,707,161) discloses a ball valve wherein the ball has a removable insert threadedly engaged within the flow passage. Also disclosed is an alternate embodiment in which the opening for the inserted choke tube is adjustable, accomplished with a threaded stem located at the bottom of the valve body.
Kindersley (U.S. Pat. No. 3,985,150) discloses a valve assembly for use with abrasive fluids wherein the valve bore has an abrasion resistant insert. The inserts may comprise ceramics (aluminum oxide, silicon carbide, boron carbide), metals (chrome alloys), rubber, or synthetic plastics (urethanes). Throttling the valve is achieved by rotating the ball, producing a reduced bore opening.
Marandi (U.S. Pat. No. 5,937,890) discloses ball valve inserts for controlling fluid flow. The inserts are preferably parabolic (convex) in shape, corresponding to the shape of the ball, providing a substantially equal percentage flow characteristic between maximum and minimum flow rate conditions. The parabolic shape of the insert compensates for the arcuate or non-linear path traveled by the insert during throttling.
Green (U.S. patent application Ser. No. 10/352,329) discloses a ball valve adapted to receive threaded inserts which may be secured to the valve by various means, including a retaining ring, press fitting, gluing, soldering, or threads. The combination of the standard ball valve and the inserts provide an infinite range of valve flow coefficients that are lower than the valve's maximum rated flow coefficient, depending on the diameter of the orifice. A disclosed advantage is stated as being retrofittable, although this requires removing the valve, selecting and inserting the desired insert for a desired flow coefficient, and reinserting the valve in the line.
Scaramucci (U.S. Pat. No. 3,542,338) discloses a ball valve adapted for throttling having a bore treated or lined with an erosion resistant material. Scott (U.S. Pat. No. 3,794,071) discloses a brake control valve device, wherein the device is equipped with a choke. Berchem (U.S. Pat. No. 5,205,533) discloses a ball valve having a ceramic coated passage and a restriction within the ball, wherein the bore within the ball narrows, producing a larger outlet bore diameter than the inlet bore.
Booth et al. (U.S. Pat. No. 5,551,467) and Lester et al (U.S. Pat. No. 5,593,135) disclose ball valves for precise throttling of fluid through the valve, achieving near linear performance in controlling the flow of the fluid. Chowdhury (U.S. Pat. No. 6,260,820) discloses a valve and method for producing the valve. Hayduk (U.S. Pat. No. 6,412,756) discloses a gas tight ball valve for use with granular material.
Guerra (U.S. Pat. No. 6,540,206) discloses a bi-directional ball valve for use with cold gases, featuring a through hole on its side surface, which in the closed position is available for the passage of fluid. The hole appears to have a greatly reduced bore diameter as compared with the main flow path. Milberger et al. (U.S. patent application Ser. No. 10/137,219) disclose a ball valve for use in oil and gas production systems, having a vent bore for the venting of pressure.